SEATTLE — The US Army said Wednesday that it will seek the death penalty against the soldier accused of killing 16 ­Afghan villagers in a predawn rampage in March, a decision his lawyer called ‘‘totally irresponsible.’’

The announcement followed a pretrial hearing last month for Staff Sergeant Robert Bales, 39, who faces premeditated murder and other charges in the attack on two villages in southern Afghanistan.

The slayings drew such angry protests that the US temporarily halted combat operations in Afghanistan, and it was three weeks before American investigators could reach the crime scenes.

Prosecutors said Bales left his
base early on March 11, attacked one village and returned to the base, then slipped away again to attack another nearby compound. Of the 16 people killed, nine were children.

No date has been set for his court-martial, which will be held at Joint Base Lewis-McChord south of Seattle.

His civilian lawyer, John Henry Browne, said he met with Army officials last week to argue his client should not face the possibility of the death penalty, given that Bales was serving his fourth deployment in a war zone when the killings occurred.

‘‘The Army is not taking responsibility for Sergeant Bales and other soldiers that the Army knowingly sends into combat situations with diagnosed PTSD, concussive head injuries, and other injuries,’’ Browne said. ‘‘The Army is trying to take the focus off the failure of its decisions, and the failure of the war itself, and making Sergeant Bales out to be a rogue soldier.’’

Shooting

Bales’s wife, Kari Bales, said she and their children have been enjoying weekend visits with Bales at Joint Base Lewis-McChord, and she hopes he receives an impartial trial.

‘‘I no longer know if a fair trial for Bob is possible, but it very much is my hope, and I will have faith,’’ she said.

Bales’s defense team has said the government’s case is incomplete, and outside specialists have said a key issue going forward will be to determine if Bales suffered from post-traumatic stress disorder. Bales grew up in Norwood, Ohio, and served tours of duty in Iraq and Afghanistan.

For Bales to face execution, the court-martial jury must unanimously find him guilty of premeditated murder. They also must determine that at least one aggravating factor applies, such as multiple or child victims, and that the aggravating factor outweighs any mitigating circumstances.

The US military has not executed anyone since 1961.

The case against Bales is being prosecuted as Western forces continue to draw down their forces and turn over responsibility for security to the Afghan government.

During last month’s preliminary hearing, prosecutors built a strong eyewitness case against Bales, with troops recounting how they saw him return to the base alone, covered in blood.

One soldier testified that Bales woke him up, saying he had just shot people at one village and that he was heading out again to attack another. The soldier said he did not believe Bales and went back to sleep.

Afghan witnesses questioned via a video link from a base near Kandahar City described the horror of that night. A teenage boy recalled how the gunman kept firing as children scrambled, yelling: ‘‘We are children! We are children!’’